refs #18442 [finc] introduce externalLinks ViewHelper

* externalize generation of off site links
* add target = _blank and rel=noopener to all external links
* set standard value for $translateLabel to false
* set merging order for parameters, so rel and target may be overwritten

module/finc/src/finc/View/Helper/Root/ExternalLink.php

+<?php
+/**
+ * External link view helper
+ *
+ * PHP version 7
+ *
+ * Copyright (C) Leipzig University Library 2020.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category VuFind
+ * @package  View_Helpers
+ * @author   Dorian Merz <merz@ub.uni-leipzig.de>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org/wiki/development Wiki
+ */
+namespace finc\View\Helper\Root;
+
+/**
+ * External link view helper
+ *
+ * @category VuFind
+ * @package  View_Helpers
+ * @author   Dorian Merz <merz@ub.uni-leipzig.de>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org/wiki/development Wiki
+ */
+class ExternalLink extends \Zend\View\Helper\AbstractHelper
+{
+    /**
+     * Context view helper
+     *
+     * @var \VuFind\View\Helper\Root\Translate
+     */
+    protected $translator;
+
+    /**
+     * Default html attributes for external links
+     *
+     * @var string[]
+     */
+    protected $defaultAttributes = [
+        'target' => "_blank",
+        'rel' => 'noopener'
+    ];
+
+    /**
+     * Renders an anchor element (hyperlink) to an external website
+     *
+     * @param string $href           URL of the external website
+     * @param string $label          desired label or translation token
+     * @param array  $attributes     more attributes to apply to the a element,
+     *                               key-value-pairs
+     * @param bool   $translateLabel true if label shall be translated
+     *
+     * @return string
+     */
+    public function __invoke(
+        $href,
+        $label = '',
+        $attributes = [],
+        $translateLabel = false
+    ) {
+        $link = '<a href="' . $href . '"';
+        $attributes = array_merge($this->defaultAttributes, $attributes);
+        foreach ($attributes as $key => $value) {
+            $link .= ' ' . $key . '="' . $value . '"';
+        }
+        $link .= '>';
+        if (empty($label)) {
+            $label = $href;
+        } elseif ($translateLabel) {
+            $label = $this->translate($label);
+        }
+        $link .= $label . '</a>';
+
+        return $link;
+    }
+
+    /**
+     * Helper function to provide access to Translate ViewHelper
+     *
+     * @param string $label translation token
+     *
+     * @return string
+     */
+    protected function translate($label)
+    {
+        if (!isset($this->translator)) {
+            $this->translator = $this->getView()->plugin('translate');
+        }
+        return $this->translator->translate($label);
+    }
+}

module/finc/src/finc/View/Helper/Root/Factory.php

@@ -151,7 +151,8 @@ class Factory
         // constructor
         if (file_exists(
             \VuFind\Config\Locator::getConfigPath('OpenUrlRules.json')
-        )) {
+        )
+        ) {
             $openUrlRules = json_decode(
                 file_get_contents(
                     \VuFind\Config\Locator::getConfigPath('OpenUrlRules.json')
@@ -194,7 +195,8 @@ class Factory
         // constructor
         if (file_exists(
             \VuFind\Config\Locator::getConfigPath('ExternalCatalogue.json')
-        )) {
+        )
+        ) {
             $externalAccessLinks = json_decode(
                 file_get_contents(
                     \VuFind\Config\Locator::getConfigPath('ExternalCatalogue.json')
@@ -209,9 +211,26 @@ class Factory
         );
     }
 
+    /**
+     * Construct Head Title Helper
+     *
+     * @param ContainerInterface $container Service manager
+     *
+     * @return HeadTitle
+     */
     public static function getHeadTitle(ContainerInterface $container)
     {
         $config = $container->get('VuFind\Config')->get('config')->Site;
         return new HeadTitle($config->title ?? '');
     }
+
+    /**
+     * Construct ExternalLink
+     *
+     * @return ExternalLink
+     */
+    public static function getExternalLink()
+    {
+        return new ExternalLink();
+    }
 }

themes/finc/theme.config.php

@@ -18,6 +18,7 @@ return [
             'record' => 'finc\View\Helper\Root\Record',
             'flashmessages' => 'finc\View\Helper\Root\Flashmessages',
             'headTitle' => 'finc\View\Helper\Root\HeadTitle',
+            'externalLink' => 'finc\View\Helper\Root\ExternalLink',
         ],
         'factories' => [
             'finc\View\Helper\Root\BranchInfo' =>
@@ -44,6 +45,8 @@ return [
                 'VuFind\View\Helper\Root\FlashmessagesFactory',
             'finc\View\Helper\Root\HeadTitle' =>
                 'finc\View\Helper\Root\Factory::getHeadTitle',
+            'finc\View\Helper\Root\ExternalLink' =>
+                'finc\View\Helper\Root\Factory::getExternalLink',
         ]
     ]
 ];